Self-powered electrical sensors are used to detect and monitor one or more characteristics of an electrical signal in a conductor. As such, self-powered electrical sensors can be used in systems to monitor current levels, voltage levels, power levels, or other aspects of an electrical system. Monitoring one or more electrical signals in an electrical system provides information on the operating conditions of the system, a subsystem, or one or more components in the system. For example, a self-powered current sensor may be used in control systems in manufacturing and industrial applications. In such applications, a self-powered current sensor may be used to monitor equipment status, to detect process variations, and to ensure safety of personnel. In addition, a self-powered current sensor may be used to control pumps, compressors, heaters, conveyors, and other electrically powered devices.
Some self-powered current sensors are equipped with an alarm that is activated upon a current in a conductor reaching a certain magnitude. The alarm trip point is set based on an adjustment. Deriving power from the electrical signal that the self-powered current sensor is monitoring prevents present self-powered current sensors from including certain functionality. For example, present self-powered current sensors include an adjustment to set a trip-point value for an alarm with a non-linear response over the range of the adjustment. Because the adjustment has a non-linear response the exact value of the adjustment cannot be easily determined. As such, an installer must set a trip point using the non-linear adjustment and then test the current sensor to ensure the trip point is set at the correct value.
So, once the self-powered current sensor has been manually adjusted, the present self-powered current sensors must be tested. The testing requires shutting a system down to adjust the sensor manually and turning the system back on to verify that the sensor had been adjusted to the proper setting. This is repeated until the self-powered current sensor is properly configured. Alternatively, the self-powered current sensor can be calibrated off site but the system still must be shut down to reinstall the current sensor and must again be verified that it is configured properly, which includes turning the system back on and if necessary shutting it down again to reconfigure the electrical sensor. Such a process of adjusting and testing present self-powered current sensors creates extended down time for a system and adds to the cost of running the system.
The correct trip-point value must be set appropriately to ensure that the alarm on a self-powered current sensor trips at a desired value to ensure equipment or a process is operating as required. Failure of an alarm to trip at the right value can result in damage to equipment, injury to personnel, or inefficiencies in a process. Any of these would result in negative consequences and add significant costs.